More recently, IL-21 has been found to be involved in several mechanisms related to RA pathogenesis being able to activate T cells, B cells, monocytes/macrophages and synovial fibroblasts through activation of JAK-STAT, MAPK, and PI3K/Akt signalling pathways, ultimately promoting osteoclastogenesis (32). This evidence concerns the gene SOAT1 and rheumatoid arthritis.